Available in the prior art is a semiconductor device illustrated in FIG. 1. Referring to the drawing, a semiconductor pellet 22 in which at least one semiconductor device element has been produced, is mounted on a printed circuit board 11 made of a glass epoxy resin complex et al. and which has bonding pads 20 thereon connected by bonding wires 26 with the counter parts 24 produced on the semiconductor pellets 22, which are covered by a resin layer 28. The printed circuit board 11 has solder bump electrodes 16 produced thereunder. When such a semiconductor device is mounted on a larger printed circuit board or a mother board 14, as is shown in FIG. 2, the solder bump electrodes 16 are connected, employing a melting process, with corresponding electrodes 50 printed on the larger printed                circuit board or the mother board 14.        
The foregoing semiconductor device available in the prior art is inevitably accompanied by drawbacks tabulated below.    1. The adhesion is inclined to be broken for the interface between the semiconductor pellets 22 and the resin layer 28, due to thermal stress caused by the difference in the coefficients of thermal expansion. This drawback readily happens during the process for mounting the semiconductor device on the larger printed circuit board or the mother board. This drawback readily allows humidity to contact metal parts of the circuit of the semiconductor pellets 22, resultantly causing the metal parts of the circuit to be corroded.    2. The heat generated in the semiconductor pellets 22 is dissipated toward the larger printed circuit board or the mother board through the printed circuit board 11 made of the glass epoxy resin complex et al. of which the thermal conductivity is less, resultantly causing a less grade of the thermal dissipation efficiency for the semiconductor device having the foregoing structure. This drawback readily causes a remarkable rate of delay in the operation speed of the semiconductor device.